Problem with this chart is it's missing US visitors, so it doesn't tell you all that much about the overall impact.
But man, the argument isn't some grassroots boycott of the US tourism industry. The argument is that going to an authoritarian country with a mass incarceration habit when you don't actually have to is a terrible idea. European countries are issuing travel warnings for people. ICE is detaining travellers with valid visas.
Just stay safe, the tourism industry boycott takes care of itself if you do.
10 to 15% is the entire margin of a lot of business in the service industry, don't underestimate the movement. Even 5% is enough to dent the stock growth of the hotel industry. That data also predate the important budget blockage of the national parks and forestry
Foreign tourists bring in foreign money, which helps balance the trade deficit.
By itself it wont be a massive impact, but combine it with many other small to medium impacts and the load on the empire will become challenging to bear more and more.