Hello @Matthewa100,
The issue with American bars/restaurants is that when you pay for the goods and leave a tip, they will take two transactions: one for the goods, and one for the goods+tip. Both transactions will be shown as pending in Revolut, with the goods+tip amount completing and the former amount reverting within 10 working days.
More info here: http://revolutapp.tumblr.com/post/151098550182/tips-taking-revolut-stateside
Best,
Andreas K.