Yea, as legalregal pointed out, it does depend on the firm. Some US firms are facing transactional pressure (economic downturns, etc.) while others are facing increased pressure from governmental agencies (think like white collar crime firms who are currently dealing with hyper-aggressive governmental regulators). Then you have your conventional, but important issues, such as the issue of cybersecurity -- US firms due to their clients and influence -- makes them key targets to attack. There is also a poaching war amplified amongst key US law firms as they battle against each other to take specialists in certain fields. Tech infrastructure is also quite a common issue - some US law firms are quite lacking in this sector.
Good luck with the interview!