In Twilight Struggle, can I place influence in countries that border my superpower?

Question

For instance, as the US, I want to place influence in Mexico. The only other influence I have in Central America is in Panama, a few spaces away.

Thematically this seems obvious, yes. They're directly connected to me. But I don't get a precise answer from the rule book.

The rules say the following [my emphasis]:

6.1.1 Influence markers are placed one at a time. However, all markers must be placed with, or adjacent to, friendly markers that were in place at the start of the phasing player’s Action Round.

Does the superpower space count as a friendly marker? According to 2.1.6, it is adjacent

2.1.6 Countries are connected to one another via the black, red and brown lines on the map. Brown lines represent connections within a region. Red dashed lines represent connections between countries in different regions. The black lines indicate connections between countries and superpowers. A country is considered adjacent to all other countries to which it is connected.

I don't see a definition of "friendly" elsewhere in the rules.

Answer 1

Upon closer inspection of the rules, I found the answer:

6.1.4 Influence markers may always be placed in any country that is adjacent (connected) to the phasing player’s superpower space.

So, yes, the US player can place influence in Mexico, just because it's adjacent.