OK, I'll humour you for a minute since I'm waiting for CI... (I am from London and live in the US, and do not agree it is more multicultural, but OK, whatever).
Let's take a single state: Texas. Population in 2017 was 28.29 million. Per the CDC [1], there were 3513 gun deaths in Texas that year. I believe this includes suicides, so let's take a conservative rate here and assume that 40% were homicides and 60% were suicide (I believe that this is over-estimating suicide).
So, 1405 gun-related homicides in Texas that year. But, Texas only has around half the population of England and Wales. I'm sure you can do the rest of the math yourself.
But, maybe Texas isn't to your liking because it's so big by land area - so let's also look at Alabama, which is approximately the same size. 1124 gun related deaths there per [1] in 2017, and conservatively assuming 40% of those were homicides, that is approximately 450. However, the population of Alabama was less than _just Greater London_ - only 4.87 million people.
But, maybe Alabama isn't to your liking either because it's conservative. So let's look at New Jersey - only just larger than Wales by land area, and substantially smaller than England, but trending "liberal" by US standards.
In NJ, there were 478 firearm-related deaths in 2017. Again if we conservatively assume 40% homicide, that's around 191 - finally a state where the absolute number is less than knife-related deaths in England and Wales! But, one where the population was only 8.8 million...
None of these include knife crime in the US, either. While you can make all the excuses you like for this, the numbers don't look very good regardless of how you cut (or shoot) it.
[1]: https://www.cdc.gov/nchs/pressroom/sosmap/firearm_mortality/...