The media, unfortunately, presents it this way.
Checks and balances are happening. They just don't get press. And it isn't just Democrats. Republicans hold the constitution almost as a sacred text. They are loyal to this document, not the President.
Are there MAGA extremists who would follow Trump into authoritarianism? Sure. But they do not represent the majority of Americans or even conservatives.
In the States, conservatives oppose federal power all the time. The feds own most of the land in several states. This is nonsense and conservative Republicans lead the charge against the federal overreach.
So are Republicans "silent" on Trump? Yes. But this isn't surprising. Political parties like to resolve their problems internally. And many of us are lobbying Senators and congresspeople to do their jobs and introduce legislation to curb Presidential power.
A similar thing happened in 2006. Americans were not comfortable with W's power grabs. So they voted for democrats to control the House. This was a clear check on Presidential power.
For some reason, there is an impression that the US president can behave with impunity. This simply isn't true. In MN, for example, the governor controls the National Guard. And this Guard is meant to preserve State power over federal influence. So will MN guard troops be deployed to oppose federal authority? Probably. And that's the way the system is supposed to work.
Also, sorry to ramble. But another important point is that the US military is not a united force. The Army, Navy, Marines, etc. are separate entities with their own chiefs and generals. So let's say Trump somehow convinces the Army that they should become loyal to him. Do we really think the Marines, AF, and Navy would tolerate this? Absolutely not. Consolidating the support of all US armed forces would be absurdly difficult by design. Rivalry between these branches is encouraged. They are meant to oppose each other if necessary. US soldiers pledge allegiance to the constitution, not a President.