US stock markets are under some heavy pressure today with the S&P 500 down 1.5% and the Russell 2000 down 2.5%.Some worries have been building for awhile and at the moment I don't think it's one single thing. It's a collection of things in an over-leveraged, overcrowded market that's led to some (overdue?) profit taking.Today's UMich long-term inflation expectations rose to the highest in 30 years, raising questions about whether the Fed should be cutting rates at allWalmart has been hit hard this week after earnings with shares down 10% from last week's record high. The company talked about a resilient consumer but also talked about consumers trading down. It doesn't take much when shares were trading at 33x earnings. Note that Amazon has also seen a similar fall. The tariff talk continues. I think it's all a bluff but that's a tough call to make when there is a fresh threat daily. Even the talk itself is problematic and appears to be hurting consumer sentiment. It's also not going away any time soon.What will Congress do? When Republicans swept the election in November there was some real enthusiasm about extending Trump tax cuts and maybe even furthering them. Now it's time to do the math and it's tough, especially with narrow margins in the House and Senate. I think the 2017 cuts get extended but that's it and there will be some grandstanding from fiscal hawks that could upend the agenda and cause some real market worries before anything gets done.Valuations. US stocks aren't cheap and the swoon in Palantir this week was a reminder that anything at 100x sales can dive at any moment. Tesla is also struggling today as Elon Musk continues to do whatever he's doing. But more broadly, there are some challenging valuations in the US and if any of the things above go wrong, it's a long way down before valuations are compelling again.Geopolitics. I tend to see a resolution of Russia-Ukraine as more of an upside risk but if it leads to some real panic in Europe about defense and heavy deficit spending then it could all go wrong quickly. The jump German defense company shares isn't exactly a 'peace trade'. There is an unsettling feeling around the US at the moment that argues for caution. I'd say this is a small factor in the risk-off mood but it's there.Everything AI. You won't find a bigger AI bull than me. I think it's a total gamechanger in macro ways that people aren't even contemplating but the questions are fair. Why hasn't AI 'discovered' anything new yet? Will it end up being more like a more-efficient Google search engine than something that provides revolutionary insight? What's the ROI on spending trillions of capex on that? I think the killer app (literally and figuratively) will be robotics but the timeline on that could be stretched. When valuations are high, markets get impatient.Rotation. Investors look for ways to avoid or mitigate these risks and that has people focusing outside of the US, where there is value in some beat-up markets. China has had an incredible month and many of the stocks there are focused domestically and insulated from tariffs. European shares have done well too despite ongoing dismal economic data. That's a sign that money is being pulled out of the US and deployed elsewhere. There is an election in Germany this weekend and high hopes for China stimulus in early March. Watch those spots carefully. This article was written by Adam Button at www.forexlive.com.