diff --git a/awscli/botocore/awsrequest.py b/awscli/botocore/awsrequest.py
index 4ce0449..2b14009 100644
--- a/awscli/botocore/awsrequest.py
+++ b/awscli/botocore/awsrequest.py
@@ -14,6 +14,7 @@
 import functools
 import io
 import logging
+from collections.abc import Mapping
 import socket
 import sys
 
@@ -24,6 +25,7 @@ from botocore.compat import (
     HTTPResponse,
     MutableMapping,
     urlencode,
+    urlparse,
     urlsplit,
     urlunsplit,
 )
@@ -66,32 +68,34 @@ class AWSConnection:
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self._original_response_cls = self.response_class
-        # We'd ideally hook into httplib's states, but they're all
-        # __mangled_vars so we use our own state var.  This variable is set
-        # when we receive an early response from the server.  If this value is
-        # set to True, any calls to send() are noops.  This value is reset to
-        # false every time _send_request is called.  This is to workaround the
-        # fact that py2.6 (and only py2.6) has a separate send() call for the
-        # body in _send_request, as opposed to endheaders(), which is where the
-        # body is sent in all versions > 2.6.
+        # This variable is set when we receive an early response from the
+        # server. If this value is set to True, any calls to send() are noops.
+        # This value is reset to false every time _send_request is called.
+        # This is to workaround changes in urllib3 2.0 which uses separate
+        # send() calls in request() instead of delegating to endheaders(),
+        # which is where the body is sent in CPython's HTTPConnection.
         self._response_received = False
         self._expect_header_set = False
+        self._send_called = False
 
     def close(self):
         super().close()
         # Reset all of our instance state we were tracking.
         self._response_received = False
         self._expect_header_set = False
+        self._send_called = False
         self.response_class = self._original_response_cls
 
-    def _send_request(self, method, url, body, headers, *args, **kwargs):
+    def request(self, method, url, body=None, headers=None, *args, **kwargs):
+        if headers is None:
+            headers = {}
         self._response_received = False
         if headers.get('Expect', b'') == b'100-continue':
             self._expect_header_set = True
         else:
             self._expect_header_set = False
             self.response_class = self._original_response_cls
-        rval = super()._send_request(
+        rval = super().request(
             method, url, body, headers, *args, **kwargs
         )
         self._expect_header_set = False
@@ -210,10 +214,13 @@ class AWSConnection:
 
     def send(self, str):
         if self._response_received:
-            logger.debug(
-                "send() called, but reseponse already received. "
-                "Not sending data."
-            )
+            if not self._send_called:
+                # urllib3 2.0 chunks and calls send potentially
+                # thousands of times inside `request` unlike the
+                # standard library. Only log this once for sanity.
+                logger.debug("send() called, but reseponse already received. "
+                             "Not sending data.")
+            self._send_called = True
             return
         return super().send(str)
 
@@ -370,8 +377,14 @@ class AWSRequestPreparer:
     def _prepare_url(self, original):
         url = original.url
         if original.params:
-            params = urlencode(list(original.params.items()), doseq=True)
-            url = f'{url}?{params}'
+            url_parts = urlparse(url)
+            delim = '&' if url_parts.query else '?'
+            if isinstance(original.params, Mapping):
+                params_to_encode = list(original.params.items())
+            else:
+                params_to_encode = original.params
+            params = urlencode(params_to_encode, doseq=True)
+            url = delim.join((url, params))
         return url
 
     def _prepare_headers(self, original, prepared_body=None):
diff --git a/awscli/botocore/httpsession.py b/awscli/botocore/httpsession.py
index 516bb3f..25f982d 100644
--- a/awscli/botocore/httpsession.py
+++ b/awscli/botocore/httpsession.py
@@ -328,7 +328,6 @@ class URLLib3Session:
 
     def _get_pool_manager_kwargs(self, **extra_kwargs):
         pool_manager_kwargs = {
-            'strict': True,
             'timeout': self._timeout,
             'maxsize': self._max_pool_connections,
             'ssl_context': self._get_ssl_context(),
diff --git a/tests/unit/botocore/test_http_session.py b/tests/unit/botocore/test_http_session.py
index 90ed7d4..0a10c15 100644
--- a/tests/unit/botocore/test_http_session.py
+++ b/tests/unit/botocore/test_http_session.py
@@ -148,7 +148,6 @@ class TestURLLib3Session(unittest.TestCase):
 
     def _assert_manager_call(self, manager, *assert_args, **assert_kwargs):
         call_kwargs = {
-            'strict': True,
             'maxsize': mock.ANY,
             'timeout': mock.ANY,
             'ssl_context': mock.ANY,