Turns out your ISP is not a tiny ISP. It is somewhat unclear what parts were sold when brightspeed was created/renamed.
Brightspeed is actually a combination of a bunch of fairly major ISP. Level3 being the largest. They also acquired century link as well as qwest. They used to be called luman.
So riotgames actually uses level 3 as their major provider of ISP servers. This link show the ISP the peer with. Many are international ISP.
https://bgp.he.net/AS6507
What this means is your ISP directly sells service to Riotgames. It is obviously a completely different division than the one that run your house.
So this tool lets you actually issue some commands from the routers in your ISP network (ie level3). Note you will get a warning because they are using HTTP rather than HTTPS. It is not a security issue unless you are going to type something other than IP addresses into their web page.
lookingglass.level3.net
I ran a tracert from their router in washington dc. You will notice it matches your trace exactly starting in hop 6. I suspect the router in hop 5 of your trace is actually the router I ran the trace from.
WASHINGTON DC USA Traceroute results for: 104.160.131.3 (104.160.131.3)
Tracing route to 104.160.131.3 1 0.0.0.0 (0.0.0.0) * * *
2 RIOT-GAMES.bear1.Washington111.Level3.net (4.14.103.174) 1ms 1ms 1ms
3 ae3.er02.chi01.riotdirect.net (104.160.159.126) 60ms 60ms 60ms
4 ae2.er02.lax01.riotdirect.net (104.160.159.186) 60ms 60ms 60ms
5 ae1.er01.lax01.riotdirect.net (104.160.151.134) 59ms 59ms 60ms
6 104.160.141.51 (104.160.141.51) 57ms 57ms 57ms
7 0.0.0.0 (0.0.0.0) * * *
8 0.0.0.0 (0.0.0.0) * * *
=======================================
You can play around with some more traces from other locations but I am not sure what you can do.
I strongly suspect this is a firewall in riotgames network blocking the traffic. It just means the tracert tools are not valid test tools to determine why something doesn't work. Your traffic obviously can get deep into riots network.
I seriously doubt there is any major routing issue between riotgames and their largest internet provider.