Bootstrap输入字段宽度太小

Question

我尝试更改用户名和密码的输入字段的宽度。但似乎没有任何事情发生

                <li class="nav-item dropdown">
                    <a class="nav-link dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"><i class="fa fa-sign-in"></i> Login </a>
                    <form class="dropdown-menu p-4 dropdown-menu-right" method="post" action="#">
                        {% csrf_token %}
                        <div class="container">
                            <div class="form-group col-xs-4">
                                <label for="username">Username:</label>
                                <input type="text" class="form-control" id="username">
                            </div>
                            <div class="form-group col-xs-4">
                                <label for="password">Password:</label>
                                <input type="password" class="form-control" id="password">
                            </div>
                            <button type="submit" class="btn btn-primary">Login</button>
                        </div>
                    </form>
                </li>