|possibly (c) COFDA|
Guam is part of the so-called "Second island chain" that kind of encircles the PR China on the ocean. It hosts a large active air base, an almost as large long since deactivated air base, a commercial airport that used to be a military airbase (1943-1995) and a tiny naval airfield from WW2 close to the port that might still be used for emergency landings (if nets were installed to stop planes that lack arresting hooks) and for take-off of lightly loaded fighters. The port itself has a huge area protected from the sea, but few facilities. It's deep enough even for a CVN, though.
(population ~ 162k)
So far my casual looks at satellite imagery didn't show substantial changes, but I didn't compare old and new imagery carefully. It can be told that the 2nd large airbase is not in use yet, though. B-52s can be seen on almost all imagery of the main airbase.
The efforts to turn the island with its small population into a kind of air-sea power fortress with a brigade equivalent of land forces is running into trouble anyway:
(nice bird's view on the main airbase there)
It's interesting to see that 4+ years after the "pivot to East Asia" and after years of talk about "island chains" very little actually changed there. One could have expected multiple installation with navy air defence and sea attack missiles, some SPG battalion with anti-ship fire controls, a reactivation of all previously existing airbases, new runway pavements, new aircraft shelters, additional port facilities et cetera. Instead, most changes required to turn the island into a kind of fortress appear to exist on paper only, even after four years.
Maybe the inhabitants are right; to turn the island into a powerful base would amass so many military assets on it that a nuclear strike would become a really enticing option in case of conflict. This in turn might deter the amassing of military assets, and just maybe the island is for this reason not even close to as important as often implied or claimed directly.
The Japanese had a similar experience with Rabaul in the Second World War: Initially an important base meant to enable further southward expansion, Rabaul soon became more of a burden than an asset to the Japanese because it was in range of U.S. air power from Port Moresby and Guadalcanal/Lunga. It lost its importance as a naval base, and the IJN's fleet assets used the safer, more remote Truk atoll as their base instead.