It's not just Republicans. An AP poll prior to US involvement said that only 26% of Americans supported a major role for the US in the Ukraine-Russia conflict. Twenty percent said we should have no role at all and 52% said only a minor role. Only 32% of Democrats thought the US should have a major role. Also, a declining percentage of Americans approved of the way Biden is handling the US relationship with Russia, also from AP.
Americans, not just Republicans, are more focused on domestic issues which the Biden admin is addressing poorly or not at all. Americans are particularly focused on economic issues, including rising inflation. Biden tells us that sanctions against Russia and support for Ukraine are going to be expensive for Americans, in terms of more inflation, higher fuel costs, and shortages. We don't seem to like that.
There is widespread public skepticism of the U.S. intelligence community, which is pushing more US involvement.
The administration promotes the idea that if Russia succeeds in Ukraine, they will begin a march across Europe. The pushback is that Putin seems more interested in getting the USSR band back together. Also, many feel that Russia lacks the resources to engage NATO countries or anyone else after this. The Russian public is known to oppose expansion efforts.
The idea that the Ukraine is a great democratic nation is heavily flawed. It remains the world capital of money laundering and child trafficking. It should come as no surprise that many Americans oppose these practices. We particularly oppose the idea that the administration may be using this funding campaign to launder money back to US and Ukrainian politicians as well as the Military/Industrial complex.
Some argue that the US is mainly sending outdated military equipment to Ukraine that is scheduled for retirement. The fact that we aren't being told how the funding works, drives skepticism. We don't know how much of the support is in the form of funding and how much is in military equipment.
People also hear that US military equipment sent to the Ukraine military is being sold on the black market as part of a money laundering process. The lack of transparency or accountability from the Biden administration, while consistently committing more and more funds and resources to the proxy war, only feeds that skepticism.
This article provides more information on why Republicans oppose more support for the Ukraine government.
Domestic Opposition to Ukraine War Intensifies