Why is she in EVERY British detective show shipped over to the US?

I really liked her role in Last Tango in Halifax, but have not been so impressed since. On one hand, she is intense and real, but the biggest problem is she swallows her lines. I have to use close captioning all the time to understand her. It’s not the British accent either because I don’t have that problem with any other British actor in films or shows, except for the odd Scottish or Geordie secondary characters.