Here are a few data points I pulled from the Akamai “State of the Internet”, 2017 Q1 PDF.
The global average connection speed increased 2.3% quarter-over-quarter to 7.2 Mbps
Page 3
Insert a general warning about “averages” here. A little further down, on page 12, they do break it down further by providing the top 10 countries:
This puts the US at ~2.6 times higher than the global average. Then I found a table on page 15 that was ever more useful:
My take away: 52% of US connections are less than 15 Mbps. Let that sink in for minute. There is an entire section, starting on page 17, that goes into more detail on US connections.
It is worth at least skimming through the ~55 pages, especially the mobile section starting on page 43.