A ger bringing bikurim - the promise of a share in Eretz Yisrael

As we discussed, R' Shachter explained that the dispute between the Chachamei Tzorfas and the Ramban was not whether the Avos had a din ben noach or yisrael, but whether they had the din of yisrael as a nation (for which yichus follows the mother) or just a shem mishpachas yisrael (for which yichus follows the father). I thought this might answer a kashe of the Mishne l'Melech. The Rambam paskens like Rabbi Yehudah that a ger is permitted to read the parsha of bikkurim despite the reference in the parsha to the promise of Eretz Yisrael - this promise is inapplicable to a ger who receives no cheilek in Eretz Yisrael. The Rambam seems to contradict himself, as with respect to viduy ma’asrot the Rambam paskens that a ger is not permitted to read the parsha because of its reference to our share in Eretz Yisrael. Perhaps one could distinguish between the two parshiyot. With respect to bikkurim, the parsha references the land ‘asher nishbata l’avoteinu’, promised to our forefathers, to mishpachas yisrael. However, the parsha of viduy ma’asrot references ‘ubareich es amcha…v’es ha’aretz asher nasata lanu’, the nation of Klal Yisrael and the land promised to us. The Rambam paskens that a ger can read the parsha of bikkurim because a ger is included retroactively in mishpachas yisrael based on the principle that Avraham was ‘av hamon goyim’. However, a ger is not retroactively a member of Klal Yisrael as a nation - ‘ger shenitgayer k’katan shenolad’, geirus is like a new birth. Therefore, the ger is excluded from viduy ma'asrot which references am yisrael as a nation.